Date: Sun, 16 Feb 1997 19:22:31 -0700 (MST) From: Charles Mott <cmott@srv.net> To: freebsd-chat@freebsd.org Subject: Countering stack overflow Message-ID: <Pine.BSF.3.91.970216191027.1528A-100000@darkstar>
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What I have noticed running test programs is that the top of the stack always appears to be at or near 0xffffffff. I am interested in generating an experimental kernel patch (for 2.1.0-R) which would randomly change the top stack address over a range of 0x4fffffff 0xffffffff when a a new process (not a fork) is started. My guess is that this will practically shut down any stack overflow attacks which gain root privilege. They may still cause crashes or process termination, though. Please advise if there is a conceptual error in what I want to do. I have to stop at the library and check out a copy of Leffler et al to get an overview, but I seem to remember that I might have to do something with the exec() call. Does an executable a.out format specify how the stack pointer is initialized, or does the OS do this? Charles Motthome | help
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